Auto body repair & detailing: Black Goo from under doors, drain holes, rust protection

Question
I have 03 Corolla (purchased new) and have for past year noticed black streaks running down the car from under the doors.  Female, age 77, I decided to check out.  I noticed at the bottom of each door 3 small openings from whence there was oozing a black tar-like goo.  I wiped the black goo off with paper towels and covered the openings with pieces of clear duct tape.  Then, I get people saying "there must be a reason for those openings".  Do you have any idea why this black goo should be coming out at the bottom of the doors?  Any problems sealing off those openings?  Thanks.  

Answer
  hi ethel,
     the goo you are seeing is just under coating that they spray inside the door for rust protection. it will not hurt anything. apparently when the weather is warm it must be softening up and running down through the drain holes. you should not plug the little holes, these are used for water drainage. thanks for writing.
                                      dave.......